This invention relates to carburetors and, more particularly, to apparatus for venting fuel vapors from the fuel bowl of a carburetor.
Carburetor assemblies typically include a fuel bowl holding fuel, e.g., gasoline, that is supplied to the engine on which the carburetor is installed. The gasoline gives off vapors and the presence of these vapors in the fuel bowl or bowls creates an internal bowl pressure which may result in an overly rich air-fuel mixture being produced in the carburetor and combusted in the engine.
By venting fuel vapors from the fuel bowl, the internal bowl pressure is balanced with the outside air pressure and better control over the air-fuel mixture is achieved. However, fuel vapors are continuously produced even when the engine is off and if they are continuously vented they eventually saturate the air space adjacent the carburetor's air inlet. These vapors gravitate into the carubretor's air horn and the intake manifold of the engine and may displace the air in these regions. Consequently, when the engine is next started, an overly rich air-fuel mixture is supplied to the engine which makes it more difficult to start.
Numerous bowl vent schemes have been used in previous carburetor designs to achieve bowl venting. One such scheme is shown in U.S. Pat. No. 4,157,366, issued June 5, 1979, to Ruth et al and assigned to the same assignee as the present application.
As shown therein, a bowl vent includes a valve member remotely located from an actuating device which moves the valve member through an intermediate structure. Such an arrangement while it effectively vents a fuel bowl under different engine operating conditions is mechanically complex and this may lead to failure of operation through mechanical breakdown.